Power train for an amphibious vehicle

ABSTRACT

A power train for an amphibious vehicle includes an engine and transaxle arranged North-South, driving front, rear, or all four road wheels. A power take off with optional decoupler and constant velocity joint drives marine drive means. The power take off may be taken from the input shaft of the transmission, and may use a synchronizer. The transaxle includes a differential. The rear wheels may be set back from the differential outputs, with intermediate drive by chains or belts. A sandwich type power take off may also be used. In the four wheel drive embodiment, a power take off is required from the rear differential. Decouplers may be provided in at least one wheel drive shaft on each driven axles.

The present invention relates to a power train which is particularlysuitable for use in an amphibious vehicle capable of travel on land andwater, and more particularly to a means of adapting a conventionalautomotive transaxle drive arrangement to d rive the wheels and themarine propulsion means of an amphibious vehicle. The invention alsorelates to an amphibious vehicle having such a power train.

In some automotive power train arrangements the engine has a crankshaftin line with the longitudinal axis of the vehicle, whereby the enginedrives an in-line transmission with an integral differential which istypically located between the engine and the transmission, thedifferential being connected by drive shafts to the drive wheels of thevehicle. This arrangement is commonly known as a transaxle drive and hasbeen employed in front engine, rear engine and mid engine power trainlayouts.

It is also known for transaxle power train arrangements to be adapted toprovide four wheel drive. In such known four wheel drive arrangements,the transaxle will typically drive the front wheels of the vehicle, witha power take off from the transmission driving the rear wheels of thevehicle.

The transaxle drive arrangement is currently used by several large carmanufacturers in the production of private passenger vehicles and istherefore produced in relatively high volumes, which makes thearrangement most procurable for use in an amphibious vehicle. Inchoosing a power train for a specialised low volume production vehicle,such as an amphibious vehicle, availability is an important factor.

EP 0 742 761 discloses a power train for an amphibious vehicle using afront wheel drive power train reversed, to mount the engine behind therear axle. The marine power take off is by a gearbox taken from thetiming end of the engine, opposite to the transmission mounting end.This power take off requires a number of custom designed parts to bedesigned, built, and assembled; and may require redesign and relocationof engine mounted accessories, such as the alternator drive belt. Also,the reversal of the power train may require additional gearing or othermodifications to ensure that the road wheels rotate in the required andexpected directions. The cost burdens and assembly requirements of suchadaptations are particularly unwelcome to low volume vehiclemanufacturers.

It is an object of the present invention to provide a power train for anamphibious vehicle in which a conventional transaxle drive is utilisedand adapted to drive at least one pair of road wheels and a marinepropulsion means.

According to a first aspect of the invention, there is provided powertrain for an amphibious vehicle comprising an engine and transaxle drivearranged in North-South alignment, that is with the front or timing endof the engine facing the front of the vehicle and with the engine inlongitudinal alignment with the vehicle axis, the transaxle driveincluding a transmission and differential, the differential beingadapted to provide drive to a pair of driven wheels of the vehicle, thepower train further comprising a power take off adapted to provide driveto a marine propulsion means.

Preferably, the power take off is provided by means of a drive shaftconnectable to an input shaft of the transmission. In a particularlypreferred embodiment, the drive shaft is selectively connectable to theinput shaft by means of a decoupler which may have means, such as abaulk ring, adapted to synchronize the speeds of the input shaft and thedrive shaft as the shafts are coupled. Conveniently, the decoupler maycomprise a gear wheel and synchro-mesh unit.

Alternatively, the power take off may comprise a sandwich power take offbetween the engine and the transaxle, which power take off providesdrive to the marine propulsion means. Drive may be transmitted from thesandwich power take off to the marine propulsion unit by means of a propshaft which may be connected to a drive shaft of the marine propulsionunit by a constant velocity joint.

In one embodiment, each wheel of the pair of the driven wheels is drivenby an output shaft of the differential, the arrangement being such thatthe axis of rotation of the pair of driven wheels is offset along thelength of the vehicle from the axis of rotation of the output shafts ofthe differential. In such an arrangement, drive may be transmittedbetween each said driven wheel and its respective differential outputshaft via a chain or belt drive means. Preferably, the chain or beltdrive means comprises a first sprocket mounted to the differentialoutput shaft, a second sprocket mounted to a wheel drive shaft and abelt or chain interconnecting the two sprockets to transmit drivebetween the output shaft and the wheel drive shaft.

The power take off may provide drive only to the marine propulsion meansor may provide drive to a second differential for driving a further pairof road wheels, with the drive to the marine propulsion unit being takenfrom the second differential. In an alternative arrangement forproviding a four wheel drive facility, where the power take off is asandwich power take off, a further power take off adapted to drive afurther pair of wheels of the vehicle may also be provided. Preferably,the further power take off is provided by means of a shaft which isdrivingly connectable to the transmission at a rearward end thereof, theshaft being adapted to drive a further differential for driving thefurther pair of wheels of the vehicle.

In all embodiments of the invention, the power train may be adapted suchthat the centre lines of the engine, transaxle, and marine propulsionunit are substantially aligned with each other and with the centre lineor longitudinal axis of the vehicle.

Preferably, the or each power take off is arranged rearward of theengine.

According to a second aspect of the invention, there is provided anamphibious vehicle having a power train in accordance with the firstaspect.

Several embodiments of the invention will now be described, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a plan view of a conventional power train arrangementincluding a longitudinal engine, and a transmission and differential ina transaxle arrangement for driving the front wheels of a vehicle;

FIG. 2 is a plan view of a conventional power train arrangementincluding a longitudinal engine, and a transmission and differential ina transaxle arrangement adapted for driving all four wheels of avehicle;

FIG. 3 is a plan view of a power train for an amphibious vehicle inaccordance with the present invention, in which the power train isadapted to drive the rear wheels and the marine propulsion means of anamphibious vehicle;

FIG. 4 shows a schematic section through the transaxle arrangement fordriving the rear wheels and marine propulsion means of the amphibiousvehicle as shown in FIG. 3;

FIG. 5 shows a schematic section through a prior art transaxle where thefifth gear is in a separate compartment to the other four gears;

FIG. 6 Shows a modification to the power train of FIG. 3, in which thetransaxle of FIG. 5 is adapted to provide an alternative power take offarrangement;

FIG. 7 is a plan view of a second embodiment of a power train for anamphibious vehicle in accordance with the invention, in which the powertrain is adapted to drive the rear wheels and the marine propulsionmeans of an amphibious vehicle;

FIG. 8 is a plan view of a third embodiment of a power train for anamphibious vehicle in accordance with the invention, in which the powertrain is adapted to drive the front wheels and the marine propulsionmeans of an amphibious vehicle;

FIG. 9 is a plan view of a fourth embodiment of a power train for anamphibious vehicle in accordance with the invention, in which the powertrain is adapted to drive all four wheels and the marine propulsionmeans of an amphibious vehicle;

FIG. 10 is a plan view of a fifth embodiment of a power train for anamphibious vehicle in accordance with the invention, in which the powertrain is adapted to drive the front wheels and the marine propulsionmeans of an amphibious vehicle;

FIG. 11 is a plan view of a sixth embodiment of a power train for anamphibious vehicle in accordance with the invention, in which the powertrain is adapted to drive the rear wheels and the marine propulsionmeans of an amphibious vehicle;

FIG. 12 is a plan view of an seventh embodiment of a power train for anamphibious vehicle in accordance with the invention, in which the powertrain is again adapted to drive the rear wheels and the marinepropulsion means of an amphibious vehicle; and

FIG. 13 is a plan view of a eighth and final embodiment of a power trainfor an amphibious vehicle in accordance with the invention, in which thepower train is adapted to drive all four wheels and the marinepropulsion means of an amphibious vehicle.

The same reference numerals have been used throughout the drawings todenote common components.

Referring firstly to FIG. 1, a conventional transaxle drive arrangement,generally indicated at 10, is shown driving the front wheels 14,16 of avehicle 12. An engine 18 is conventionally positioned forward of thefront wheels 14,16 with the crankshaft of the engine 18 in axialalignment with the centre line, chain dotted at 20, of the vehicle 12. Atransmission 22 is mounted in line with the engine 18 and drives adifferential 24. Drive shafts 26,28 drive the front wheels 14,16 of thevehicle from the differential 24. The rear wheels 30,32 of the vehicle12 are not driven.

A second conventional transaxle arrangement 11 for a vehicle 13 will nowbe described with reference to FIG. 2. Engine 18, transmission 22, anddifferential 24 are arranged to drive front wheels 14,16 through driveshafts 26,28 as in the arrangement of FIG. 1. In this case, however, apower take off is located at the rear of transmission 22, driving centredifferential 31 and rear differential 33. Drive shafts 27 and 29 driverear wheels 30 and 32 respectively. This arrangement is a convenient wayof offering a four wheel drive transmission in combination with a“North-South” mounted engine and transaxle as shown.

The term “North-South” will be understood by those skilled in the art toindicate a vehicle power train in which the engine is mounted so thatthe axis of the crankshaft is in alignment with or parallel to the axisof the vehicle and in which the front end of the engine, usually thetiming end, faces towards the front of the vehicle. The term should beinterpreted in this sense throughout the description and/or claims.

A first embodiment of the invention will now be described with referenceto FIGS. 3 and 4. A North-South mounted engine 18 and in linetransmission 22 are positioned at the rear of an amphibious vehicle 34,with the crankshaft of the engine 18 in axial alignment with the axis 20of the vehicle 34 and the front or timing end of the engine facingtowards the front of the vehicle. The engine 18 is positioned forward ofthe centre line of the rear wheels 30,32, and the transmission 22 drivesa differential 24 in a transaxle arrangement, as described withreference to FIG. 1. Drive shafts 26,28 drive the rear wheels 30,32 ofthe vehicle 34 from the differential 24.

Decouplers 43, 45 are provided in the drive line between thedifferential 24 and the driven road wheels 14, 16. The decouplers 43,45enable drive to the driven wheels to be decoupled when the vehicle isoperated in marine mode. Alternatively, rather than providing adecoupler 43, 45 in the drive line between the differential and eachdriven wheel, a decoupler may be provided in the drive line between thetransaxle and only one of the driven wheels 14, 16 or they may beomitted altogether.

As is best seen in FIG. 4, a power take off is provided on thetransmission to drive a marine propulsion means in the form of a waterjet 40. An impeller shaft 36 drives an impeller 38 of the water jet 40from the transmission 22. The impeller shaft 36 can be selectivelycoupled to an extension of the input shaft 44 of the transmission by adecoupler 42. Gears 46 mounted to the shaft 44 are engaged in knownmanner with corresponding gears 48 mounted on an output shaft 50, whichdrives the differential 24. The gears 46 and corresponding gears 48provide the gear ratios of the transmission 22.

In a preferred embodiment the decoupler 42 which selectively couples theinput shaft 44 of the transmission to the impeller drive shaft 36 hasmeans which are adapted to synchronise the speeds of the shafts as theyare coupled. For example, the decoupler may be of the type disclosed inthe applicants co-pending International patent applicationPCT/GB01/03493 which comprises a baulk ring for synchronizing the speedsof the shafts.

A modification to the first embodiment will now be described in relationto FIGS. 5 and 6.

FIG. 5 shows a conventional transaxle 22′ in which a fifth speed isprovided by an ‘overhung’ pair of constant mesh gears 58,60 which arepositioned in a separate compartment 61, adjacent to the maincompartment 63 of the transaxle 22′. A synchro-mesh unit 65 is employedto couple the drive gear 58 to the input shaft 44 whereby the drive gear58 and the driven gear 60 may drive the output shaft 50 and thus thedifferential 24. Similar synchro-mesh units (not shown) are convenientlyemployed to couple and decouple the gears 46 and 48 in the maincompartment 63.

FIG. 6 shows how the transaxle 22′ of FIG. 5 can be modified to providea power take off for use in the power train of FIG. 3. In the modifiedtransaxle 22″ the driven gear 60 has been removed from the output shaft50 whereby the fifth speed of the transaxle 22′ will no longer beavailable to drive the rear wheels 30, 32 of the vehicle 34. However,the drive gear 58 may still be coupled to the input shaft 44 by thesynchro-mesh unit 65, such that by coupling the fifth gear axially tothe impeller shaft drive shaft 36, as shown at 67, drive to the waterjet 40 may be provided in a manner similar to that described above inrelation to FIG. 4, with the synchro-mesh unit 65 acting as a decoupler.

This modified arrangement provides an advantage over the arrangement ofFIG. 4, in that the existing coupling system of synchro-mesh unit 65 maybe employed as a decoupler in place of the additional decoupler 42 usedin FIG. 4.

The modified power take off arrangement can of course be used with anytransaxle in which a pair of overhung gears are located in a separatecompartment of the transaxle. For example where the transaxle has asixth speed gear in a separate compartment, the sixth speed gear can beused to provide the power take off as described above.

Whilst preferred forms of the power take off have been described, itwill be understood by those skilled in the art that any suitable form ofpower take off can be used to drive the water jet 40 from thetransmission.

FIG. 7 shows a second embodiment of the invention. The arrangement issimilar to that of the first embodiment except that the engine 18 andtransmission 22 have been moved forward in the vehicle to accommodate alonger jet drive 41. The differential 24 has output drive shafts 26, 28on which are mounted sprockets 21, 23. The sprockets 21, 23 drivecorresponding sprockets 21′, 231 on offset wheel drive shafts 26′, 28′by means of a belt or chain 47, 47′. This arrangement permits drive tobe transmitted between the differential 24 and the driven wheels 30,32whose axis of rotation is offset along the length of the vehicle fromthe axis of rotation of the output shafts 26, 28 of the differential.

A decoupler 43, 45 is fitted in the drive line between the differentialand each of the driven rear wheels 30, 32 in order that drive to thewheels can be disconnected when the vehicle is used in a marine mode. Inthe present embodiment a decoupler 43, 45 is fitted in each of the wheeldrive shafts 26′, 28′ but it will be appreciated that the decouplerscould be fitted in the differential output shafts 26, 28 instead.Alternatively only a single decoupler can be used in the drive pathbetween the differential and one of the wheels. Where a single decoupleris used to disconnect drive between the differential and one of thedriven wheels 30, 32, the corresponding wheel pinion in differential 24will spin without transmitting power, while the other pinion will not bedriven. If it is found in practice that the other wheel drive shaftrotates, through transmission oil drag or whatever other reason, it maybe locked by use of the vehicle handbrake.

In a third embodiment of the invention, shown in FIG. 8, the engine 18of an amphibious vehicle 54 is mounted in the conventional position fora transaxle front wheel drive arrangement, that is forward of the centreline of the front wheels 14,16. The front wheels 14,16 are driven bydrive shafts 26,28 with at least one decoupler 43, 45 as described withreference to FIG. 3. A propeller shaft 52 is connected to a decoupler42, which is driven by the conventional input drive shaft 44 of thetransmission 22. The propeller shaft 52 is coupled to the input shaft bymeans of the decoupler 42 in a manner similar to way in which theimpeller shaft 36 is connected to the input shaft in the FIG. 4embodiment. Alternatively, the propeller shaft 52 may connected to theinput shaft by use of a fifth or sixth speed gear and synchro-mesh unitas described above in relation to FIGS. 5 and 6. The propeller shaft 52runs axially of the vehicle 54 and is connected to the impeller shaft 36by means of a constant velocity joint 56. The impeller shaft 36 drivesthe impeller 38 of the water jet 40, positioned at the rear of thevehicle 54.

FIG. 9 shows a fourth embodiment of the invention, with all four roadwheels of the vehicle 64 driven as well as a marine drive 40. It shouldbe noted that in this embodiment, the jet drive may be geared down or upaccording to the gear ratios of the transmission 22; whereas in theembodiments of FIGS. 4 and 6, the jet is driven at crankshaft speed.This embodiment generally follows the road car layout of FIG. 2, butincorporates at least one decoupler 43, 45 for the front wheel driveshafts 26, 28, and at least one decoupler 43′, 45′, for rear wheel driveshafts 27,29. In this case, rear differential 33′ incorporates a powertake off to take drive rearwards to decoupler 42 and marine drive 40. Itis not proposed to describe such a power take off in detail, becausethey are known in the power train art, for example for transmittingdrive from the second to the third axle of a 6×6 truck. It isadvantageous to use independent rear suspension with this layout, asthis will allow differential 33′ to maintain a consistent positionrelative to water jet 40. This in turn avoids any need for articulationof rearward drive shaft 25′, which would be difficult to arrangesatisfactorily in the short shaft length available.

FIG. 10 shows a fifth embodiment of the invention, with front roadwheels of the vehicle 74 driven as in the FIG. 8 embodiment, but with analternative power take off device. Engine 18 is offset forward comparedto the FIG. 8 embodiment, and a sandwich type power take off 53 isinterposed between the engine and the transaxle. Sandwich power take off53 will not be described in detail in the present application but may beconstructed according to the applicant's co-pending British patentApplication No. GB 0020884.3. The power take off 53 drives a propellershaft 62, which is necessarily installed at a lateral angle to thevehicle centre line 20. A constant velocity joint 56 is fitted, to alignthe input drive of the water jet unit 40 with its output. Decoupler 42may be fitted in the propeller shaft to enable the water jet drive to bedisengaged during road driving. A further constant velocity joint (notshown) may be fitted at the front of the propeller shaft 62, adjacent topower take off 53. The further constant velocity joint may be combinedwith a decoupler, according to the applicant's co-pending Internationalpatent application No. PCT/GB01/03493, in which case the separatedecoupler 42 can be omitted.

FIG. 11 shows a sixth embodiment of the invention. This embodiment issimilar to the first embodiment shown in FIG. 3, except that drive tothe marine propulsion unit 40 is provided from a sandwich power take off53 between the engine 18 and the transaxle. The sandwich power take offunit 53 is the same as that described above in respect of the fifthembodiment as shown in FIG. 10. Use of a sandwich power take off has theadvantage that decoupler(s) are not required in the wheel drive shafts26, 28, because the gearbox, whether manual or automatic, can be left inneutral gear when driving in marine mode. The sandwich power take off 53drives the marine propulsion unit 40 by means of a prop shaft 62′ whichis connected to a drive shaft 36 of the marine propulsion unit by aconstant velocity (CV) joint 56 because of the angle of shaft 62′. Asecond CV joint will be required adjacent to the power tale off. Thismay be combined with a decoupler 42 shown in FIG. 11. It will be notedhere that drive shaft 36 is of vestigial length, for packaging reasons.

FIG. 12 shows a seventh embodiment of the invention, where the sandwichpower take off arrangement described in relation to FIGS. 10 and 11 isapplied to the power train layout of the second embodiment of theinvention, as shown in FIG. 7.

FIG. 13 shows an eighth and final embodiment of the invention, where thesandwich power take off arrangement as shown in FIGS. 10 to 12 isapplied to the power train layout of the fourth embodiment of theinvention, as shown in FIG. 9. This layout is particularly advantageousin that it avoids the use of either two or four wheel drive shaftdecouplers.

In each of the sandwich power take off embodiments described above inrelation to FIGS. 10 to 13, a decoupler 42 is provided in the prop shaftadjacent to the power take off, and a CV joint 56 is incorporated in themarine propulsion unit. This is a preferred solution, because of controlcable packaging; but it will be appreciated that the positions of CVjoint and decoupler could be reversed if it is more convenient.

Whereas the invention has been described in relation to what ispresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not limited to thedisclosed arrangements but rather is intended to cover variousmodifications and equivalent constructions included within the spiritand scope of the invention. For example, whilst it is preferred that themarine propulsion unit should be in the form of a water jet, anysuitable marine propulsion means, such as a marine screw propeller,could be used.

1-12. (canceled)
 13. An amphibious vehicle having a plurality of roadwheels and at least one marine propulsion unit, the vehicle beingprovided with an engine arranged to drive a gearbox having an output,wherein such engine is longitudinally oriented and positioned in frontof said gearbox and such output is arranged to drive at least some ofthe road wheels and the marine propulsion unit wherein the output isarranged to drive the road wheels through a differential located betweenthe engine and the gearbox.
 14. The amphibious vehicle of claim 13,further comprising a decoupler between said gearbox output and saidmarine propulsion unit.
 15. The amphibious vehicle of claim 14, furthercomprising a decoupler between said gearbox output and said drivenwheels.
 16. The amphibious vehicle of claim 13, further comprising adecoupler between said gearbox output and said driven wheels.
 17. Theamphibious vehicle of claim 13, wherein said amphibious vehicle has fourroad wheels.
 18. The amphibious vehicle of claim 17, wherein all four ofsaid road wheels are driven.
 19. The amphibious vehicle of claim 13,wherein said gearbox and said marine propulsion unit are positionallyfixed.
 20. The amphibious vehicle of claim 19, wherein said drivenwheels are independently suspended.
 21. The amphibious vehicle of claim13, wherein said gearbox is associated with a transaxle which housessaid differential.
 22. The amphibious vehicle of claim 21, wherein saidgearbox output drives wheels through a second differential.
 23. Theamphibious vehicle of claim 22, wherein said marine propulsion unit isdriven via a power takeoff from said second differential.
 24. Theamphibious vehicle of claim 23, wherein said second differential andsaid marine propulsion unit are positionally fixed.
 25. The amphibiousvehicle of claim 24, wherein wheels driven via said second differentialare independently suspended.
 26. The amphibious vehicle of claim 13,further comprising a center differential between said gearbox output andsaid second differential.
 27. An amphibious vehicle having wheels and amarine propulsion unit rotationally driven by a longitudinally orientedengine via a variable ratio transmission, wherein said marine propulsionunit is driven by a driveshaft extending from one end of saidtransmission and said wheels are driven from the opposite end of saidtransmission, wherein both said wheels and said marine propulsion unitare drivable at selectable rotational speeds different from saidengine's rotational speed and wherein said engine, marine propulsionunit and driveshaft are coaxially arranged along a common axis.
 28. Theamphibious vehicle of claim 27, further comprising a decoupler forbetween said transmission and said marine propulsion unit.
 29. Theamphibious vehicle of claim 27, further comprising a decouplers forselectively decoupling said wheels from said transmission.
 30. Theamphibious vehicle of claim 27, wherein vehicle has a pair of frontwheels and a pair of rear wheels and said engine is positioned in frontof said rear wheels.
 31. The amphibious vehicle of claim 30, whereinsaid engine is positioned in front of said front wheels.
 32. Theamphibious vehicle of claim 27, wherein said marine propulsion unit isdriven by a non-articulating drive shaft.
 33. The amphibious vehicle ofclaim 27, wherein said driveshaft extends from the rear of saidtransmission and said wheels are driven from the front of saidtransmission.